Top U.S. law firms are adding a steadily increasing number of attorneys to their overseas offices, but most are remaining cautious about which cities to choose.

Since 2000, the 250 largest U.S.-based law firms have more than doubled their attorney ranks in Europe and increased the number of attorneys in Asia by 60 percent, mainly owing to growth in China, according to data collected in The National Law Journal‘s annual survey of the nation’s 250 largest law firms.